Mitral Stenosis, Supravalvular Ring |
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INTRODUCTION
Background: Supravalvar mitral ring is a rare congenital heart defect, of surgical importance, characterized by an abnormal ridge of connective tissue on the atrial side of the mitral valve. Often circumferential in shape, the supravalvar ring may encroach on the orifice of the mitral valve and may adhere to the mitral valve leaflets and restrict their movements. While a supravalvar mitral ring may allow normal hemodynamic flow from the left atrium to the left ventricle (LV), it often causes significant obstruction to mitral valve inflow. Although it can occur as an isolated defect, supravalvar mitral ring is found in combination with other congenital heart defects in nearly 90% of cases. Awareness of anatomic variations in patients with supravalvar mitral ring and preoperative recognition of the lesion are important.
Pathophysiology: Supravalvar mitral ring is a circumferential ridge or membrane arising from the left atrial wall overlying the mitral valve and frequently attached to the mitral valve annulus. Variable in thickness and extent, it ranges from a thin membrane to a thick discrete fibrous ridge. The membranous variety may be difficult to detect, since the membrane often adheres to the anterior mitral valve leaflet while remaining just proximal to the posterior mitral leaflet. Adhesion to the valve may impair opening movement of the leaflets, and this may be the main mechanism of mitral valve inflow obstruction in some patients. In others, the ring may be large enough to protrude into the mitral valve inflow and cause obstruction. The supramitral ring also may be incomplete and eccentric, allowing unobstructed flow through the mitral valve.
Supravalvar mitral ring rarely occurs as an isolated defect; other congenital heart defects coexist in 90% of patients. The mitral valve itself often is abnormal and stenotic at the valvar or subvalvar level with fusion of leaflets, small valve orifice, and abnormal papillary muscles being common abnormalities. Shone syndrome describes a combination of 4 congenital heart defects: supravalvar mitral ring, parachute mitral valve, subvalvar aortic stenosis, and aortic coarctation. Other common associated lesions in patients with supravalvar mitral ring are ventricular septal defect (VSD), patent ductus arteriosus (PDA), atrioventricular canal defect, and tetralogy of Fallot. Less commonly associated defects include atrial septal defect, left superior vena cava, and Wolff-Parkinson-White syndrome. Lesions such as transposition of the great arteries and double outlet right ventricle uncommonly are complicated by the presence of a supravalvar mitral ring.
Obstruction to mitral inflow results from a reduction in mitral valve orifice area. When significant, a diastolic pressure difference occurs between the left atrium and LV. Left atrial and pulmonary venous pressures increase, leading to exudation of fluid into the pulmonary interstitium, which causes increased lung stiffness. Breathlessness and tachypnea are secondary to the interstitial edema and diminished pulmonary compliance. In severe cases, frank pulmonary edema can occur. An associated atrial septal defect may decompress the left atrium, thereby reducing or masking severity of the mitral valve obstruction. Associated lesions, such as VSD or PDA, which increase LV output, will exacerbate the manifestations of mitral inflow obstruction. Conversely, supravalvar mitral ring may be difficult to detect in the presence of conditions with diminished pulmonary blood flow, such as tetralogy of Fallot.
Persistently elevated pulmonary venous hypertension leads to pulmonary arterial hypertension, a rise in pulmonary vascular resistance, and eventually, failure of the right ventricle. Tricuspid regurgitation is a common accompaniment of right heart failure from pulmonary hypertension.
Frequency:
- Internationally: No data are available on incidence of supravalvar mitral ring. In most patients, the supravalvar mitral ring is detected during investigation for other congenital heart disease (CHD).
Race: No specific race predilection exists.
Sex: No specific sex predilection exists.
Age: No specific age predilection exists.
CLINICAL
History: Supravalvar mitral ring can be diagnosed in one of the following ways:
- Supravalvar mitral ring most commonly is diagnosed as an associated finding in other CHD.
- Supravalvar mitral ring occasionally may be found as the cause of congenital mitral stenosis (MS) in symptomatic children with dyspnea or pulmonary hypertension. The severity of symptoms depends upon the level of left atrial and pulmonary venous hypertension.
- Most patients become symptomatic by age 2 years.
- Rarely, this condition may be detected as an incidental finding in asymptomatic patients undergoing echocardiography for some unrelated reason.
- Symptoms of supravalvar mitral ring with MS include one or more of the following:
- Dyspnea, nocturnal cough, and tachypnea from pulmonary venous congestion and increased lung stiffness
- Frequent respiratory infections and wheezing from pulmonary congestion, increased fluid exudation, and airway narrowing
- Poor feeding, failure to thrive, fatigue, and sweating from heart failure and reduced cardiac output
- Occasionally acute pulmonary edema or generalized edema
- Hemoptysis and syncope in older patients
Physical: Physical signs in
supravalvar mitral ring usually relate either to the associated CHD or to
pulmonary arterial hypertension. Children with significant mitral
obstruction frequently are quite sick, with tachypnea and respiratory
distress. Diminished cardiac output and poor perfusion lead to a low
volume pulse and peripheral cyanosis. Systemic venous pressure may be
elevated with the development of congestive heart failure (CHF). A
prominent parasternal heave indicates right ventricular hypertrophy from
pulmonary hypertension.
The pulmonary component of the second heart sound is accentuated, yet,
unlike acquired mitral valvar stenosis, an opening snap of the mitral
valve is not heard in supravalvar mitral ring. An apical middiastolic
murmur of MS may be audible at the apex, especially in the left lateral
decubitus, and it may exhibit presystolic accentuation. The murmur is very
prominent when supravalvar mitral ring is associated with VSD or PDA,
causing a large mitral inflow.
Patients with chronic mitral obstruction develop signs of tricuspid
regurgitation and CHF, such as hepatomegaly, engorged neck veins, large
expansile CV waves in the jugular venous pulse, and a systolic murmur that
accentuates in inspiration at the lower left sternal border.
DIFFERENTIALS
Cor Triatriatum
Mitral Valve, Double Orifice
Other Problems to be Considered:
Pulmonary hypertension, congenital heart disease
WORKUP
Lab Studies:
- No specific laboratory blood tests are required for diagnosis.
Imaging Studies:
- Imaging studies are essential to define the anatomy of the ring and mitral valve, to assess the severity of obstruction, and to identify any associated defect before undertaking surgical treatment.
- Chest x-ray
- Left atrial enlargement, the most common abnormality on chest x-ray in patients with mitral obstruction, is diagnosed by the findings of straightening of the left cardiac border (mitralization), widening of the tracheal carina, and elevation of the left bronchus. In older children, the enlarged left atrium may be seen as a double density near the right cardiac border.
- The left atrium tends to enlarge in a posterior direction. A barium-swallow study of the esophagus in lateral projection shows a rounded indentation of the anterior wall.
- Prominent upper lobe pulmonary veins, increased interstitial markings, and Kerley lines indicate pulmonary venous hypertension. In severe cases, alveolar edema produces a hazy appearance in the hilar regions of both lung fields.
- The pulmonary trunk and its branches become dilated with the rise in pulmonary arterial pressure. Cardiac contour reflects right ventricular hypertrophy.
- Echocardiography
- Two-dimensional echocardiogram with Doppler is the most important tool for the diagnosis and detailed assessment of patients with supravalvar mitral ring. It identifies the lesion and quantifies severity of the obstruction.
- Perform a systematic and diligent scan of the mitral valve and left atrium, using multiple transthoracic views and paying particular attention to evaluate all components of the mitral valve apparatus. Use parasternal, apical, and subcostal views to visualize the mitral inflow region.
- Using this technique allows the physician to view the supravalvar mitral ring and define its exact position, size, and extent, and to assess the relation of the ring to the mitral valve leaflets.
- Occasionally, a thin membrane may so closely adhere to the valve leaflets that it is difficult to demonstrate by 2-dimensional echo. With an adherent membrane, the movements of mitral valve leaflets may be impaired, characterized by diminished excursions and a flattened E-F slope on motion mode (M-mode) echo of the mitral valve.
- Inspect mitral valve chordae and papillary muscles for any associated abnormality. Exclude other associated defects, particularly subaortic stenosis, VSD, and coarctation of the aorta.
- The pulmonary artery, right ventricle, and right atrium enlarge with the development of pulmonary arterial hypertension.
- Use M-mode echocardiography of the pulmonary valve, which often shows such signs of pulmonary hypertension as an abbreviated A wave, midsystolic closure, and systolic flutter of pulmonary leaflets.
- Doppler echocardiography
- Doppler interrogation and color-flow mapping reveal the pattern of flow through the mitral valve, diagnose the presence and severity of obstruction, and demonstrate additional areas of abnormal flow in valvar or subvalvar mitral regions. The characteristic finding is turbulent flow with increased velocity across the supravalvar mitral ring into the mitral valve.
- Quantify the severity of mitral obstruction by measuring the mean velocity of diastolic flow through the mitral valve. The mean diastolic velocity as well as the pressure half-time (time taken for the peak diastolic velocity to fall to half its initial value) correlate well with the severity of obstruction.
- Measure the peak velocity of the tricuspid regurgitant jet in the right atrium for an estimate of systolic right ventricular pressure.
Other Tests:
- Transesophageal echocardiography
- Transesophageal echocardiography generally is not necessary to assess supravalvar mitral ring with obstruction in children, as adequate information can be obtained from transthoracic windows.
- In older patients, heavily built individuals, and in patients with emphysematous chests, transesophageal study can provide additional, clear views to inspect all components of the supravalvar mitral ring and mitral valve.
- Thrombi in the left atrium may be detected.
- Intraoperative transesophageal echo is useful for patients of all ages to assess adequacy of repair in the operating room.
- Electrocardiogram
- The electrocardiogram in isolated supravalvar mitral ring demonstrates left atrial enlargement, right ventricular hypertrophy, and right atrial enlargement in proportion to the degree of obstruction.
- Presence of additional defects will influence the electrocardiogram accordingly.
Procedures:
- Cardiac catheterization
- Cardiac catheterization is not necessary if echo provides all anatomic and hemodynamic data in patients with supravalvar mitral ring; however, it can provide additional information on the severity of mitral obstruction, especially in the presence of other associated CHD.
- Proximal left atrial pressure and pulmonary venous pressure both are elevated. A pressure difference can be demonstrated in diastole between the left atrium and LV. Since entry into the left atrium may be difficult and require transseptal puncture, pressure recorded in the pulmonary artery wedge position usually is a reliable indicator of left atrial pressure.
- Pulmonary artery pressure is elevated in chronic mitral obstruction. Associated shunts and other obstructive lesions also are identified and quantified at cardiac catheterization.
- Cardiac angiography
- With the availability of high-quality 2-dimensional and Doppler echocardiography, cardiac angiography has a limited role in the assessment of patients with supravalvar mitral ring. Echocardiography is superior to angiography in defining the anatomic and functional abnormality.
- Left atrial angiogram in the caudally angulated right anterior oblique view and 4-chamber view may demonstrate the supravalvar mitral ring. A closely adherent ring may, however, be difficult to visualize and differentiate from valvar mitral stenosis, since the left atrium and appendage are enlarged and clearance of contrast from the left atrium into the LV is delayed.
- An LV angiogram provides additional anatomic information about the mitral valve, ventricular septum, left ventricular outflow tract, and aortic arch.
TREATMENT
Medical Care: Evaluate patients with supravalvar mitral ring on an outpatient basis. Admit patients to the hospital for cardiac catheterization, treatment of severe heart failure or pulmonary edema, and for surgical treatment.
- Goals of medical treatment
- To relieve symptoms caused by pulmonary venous congestion and CHF
- To stabilize the patient’s condition before undertaking detailed assessment and surgical repair
- To serve as an adjunct to surgical repair in the postoperative period
- Control of heart failure by medical therapy may be the preferred option in small infants. Controlling CHF may permit deferral of surgery temporarily.
Surgical Care:
- Goals of surgical therapy
- Perform surgical repair in all symptomatic patients with supravalvar mitral stenosis to relieve the obstruction.
- Perform an early operation for supravalvar mitral ring in the presence of severe heart failure, pulmonary edema, or pulmonary arterial hypertension.
- Adjust the type of operation depending on the anatomy of the supravalvar ring and mitral valve apparatus and any associated congenital heart defect. Make every effort to define the anatomy in detail before undertaking surgery. In many patients, the supravalvar ring can be excised completely while any associated mitral valve abnormality is repaired simultaneously. If the supravalvar ring is densely adherent to the mitral valve leaflet or the mitral valve apparatus is grossly abnormal, replacement of the mitral valve may be necessary.
- Selected cases of supravalvar ring with mitral stenosis may be amenable to balloon dilatation, but results are less successful than with operation.
- Presence of a normal underlying mitral valve is associated with a better surgical outcome than with abnormal valve tissue.
- In patients who require resection at an early age the prognosis is poor. Mortality is high, with risk of recurrent supravalvar mitral stenosis in survivors, probably because of continuing turbulence across the small LV inflow tract.
Consultations: Consult a cardiologist and cardiothoracic surgeon.
Diet:
- No special diet is required in asymptomatic patients with supravalvar mitral ring.
- Advise patients to avoid excess intake of salt or to reduce salt intake in the presence of heart failure. Use salt restriction cautiously in infants.
- Restrict fluid intake to approximately 60-80 mL/kg/d in infants with CHF.
Activity: Advise patients with
pulmonary venous congestion or CHF to avoid strenuous exertion.
Asymptomatic children without pulmonary hypertension may participate in
normal activities.
MEDICATION
Medical therapy for supravalvar mitral ring
consists of drugs to control pulmonary venous congestion and cardiac
failure. The 2 main categories of medicines used are diuretics to promote
excretion of excess water and positive inotropic drugs to improve
myocardial function. Medical therapy helps to relieve symptoms of
pulmonary edema and CHF, but does not correct the underlying anatomic
problem of obstruction.
Drug Category: Diuretics -- Useful to remove excess water that accumulates in heart failure and to relieve symptoms associated with pulmonary edema and peripheral edema.
| Drug Name |
Furosemide (Lasix) -- DOC for rapid relief of pulmonary congestion and edema caused by CHF. Useful for maintenance therapy for CHF in patients with supravalvar mitral ring. Promotes renal excretion of water by inhibiting the electrolyte transport system in the ascending limb of the loop of Henle. Can increase solute and water excretion, even in the presence of a declining glomerular filtration rate. |
|---|---|
| Adult Dose | 40-320
mg/d PO in 2-3 divided doses 40-120 mg/dose IV |
| Pediatric Dose | 2-5
mg/kg/d PO divided bid/tid 1-2 mg/kg/dose IV bid/tid |
| Contraindications | Documented hypersensitivity; hepatic coma, anuria, state of severe electrolyte depletion |
| Interactions | Antagonizes muscle relaxing effect of tubocurarine; auditory toxicity appears to be increased with coadministration of aminoglycosides and furosemide; hearing loss of varying degrees may occur; possible enhanced anticoagulant activity of warfarin when taken concurrently |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Titrate dose to achieve optimal degree of diuresis without causing undue electrolyte imbalance or other adverse effects; periodically check serum electrolytes during therapy; observe for dehydration, hypokalemia, hyponatremia, hypochloremic alkalosis, hyperuricemia, hypomagnesemia, and sensorineural hearing loss |
| Drug Name |
Chlorothiazide (Diuril) -- Thiazide that causes increased excretion of water by inhibiting reabsorption of sodium chloride in the distal renal tubule; less potent diuretics than furosemide, they are useful in maintenance therapy of CHF; in severe CHF or refractory edema, thiazides act synergistically with furosemide to promote diuresis. |
|---|---|
| Adult Dose | 125-250 mg/d PO divided bid |
| Pediatric Dose | 20 mg/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity; anuria or renal decompensation |
| Interactions | Possible decreased effects of anticoagulants, antigout agents and sulfonylureas; possible increased toxicity of allopurinol, anesthetics, antineoplastics, calcium salts, loop diuretics, lithium, diazoxide, digitalis, amphotericin B, and nondepolarizing muscle relaxants |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Renal disease, hepatic disease, gout, diabetes mellitus, and erythematosus; titrate dose to achieve optimal diuresis without causing undue electrolyte imbalance or other side effects; periodically check serum electrolytes during therapy; observe for hypokalemia, hyponatremia, hypochloremic alkalosis, hyperuricemia, hypercalcemia, hypomagnesemia, hyperglycemia, rise in serum LDL cholesterol and triglyceride levels, and pancreatitis |
| Drug Name |
Hydrochlorothiazide (Esidrix, HydroDIURIL) -- Thiazide that causes increased excretion of water by inhibiting reabsorption of sodium chloride in the distal renal tubule; less potent diuretics than furosemide, they are useful in maintenance therapy of CHF; in severe CHF or refractory edema, thiazides act synergistically with furosemide to promote diuresis. |
|---|---|
| Adult Dose | 12.5-50 mg/d PO divided bid; not to exceed 200 mg/kg/d |
| Pediatric Dose | 2 mg/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity; anuria or renal decompensation |
| Interactions | Possible decreased effects of anticoagulants, antigout agents and sulfonylureas; possible increased toxicity of allopurinol, anesthetics, antineoplastics, calcium salts, loop diuretics, lithium, diazoxide, digitalis, amphotericin B, and nondepolarizing muscle relaxants |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Renal disease, hepatic disease, gout, diabetes mellitus, and erythematosus; titrate dose to achieve optimal diuresis without causing undue electrolyte imbalance or other side effects; periodically check serum electrolytes during therapy; observe for hypokalemia, hyponatremia, hypochloremic alkalosis, hyperuricemia, hypercalcemia, hypomagnesemia, hyperglycemia, rise in serum LDL cholesterol and triglyceride levels, and pancreatitis |
| Drug Name |
Spironolactone (Aldactone) -- Counteracts secondary hyperaldosteronism that occurs in cardiac failure; it inhibits sodium absorption in the collecting duct and has a potassium-sparing diuretic effect. Used alone, it produces relatively mild diuresis; however, it may be used in conjunction with furosemide for synergistic action in severe CHF. |
|---|---|
| Adult Dose | 25-100 mg/d PO divided bid |
| Pediatric Dose | 2-4 mg/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity; anuria, renal failure, hyperkalemia |
| Interactions | Possible decreased effect of anticoagulants; potassium and potassium-sparing diuretics may increase toxicity |
| Pregnancy | D - Unsafe in pregnancy |
| Precautions | Periodically check serum potassium level and renal functions; take special care when using in combination with captopril; observe for hyperkalemia, metabolic acidosis, rash, and gynecomastia |
| Drug Name |
Digoxin (Lanoxin) -- DOC among inotropic agents. It improves CHF by its positive effect on myocardial contraction. It also helps to control fast ventricular rate, especially in the presence of atrial arrhythmia. Preparations of digoxin include digoxin elixir (0.05 mg/mL) and digoxin tablets (0.125 mg or 0.25 mg each). |
|---|---|
| Adult Dose | Total
digitalizing dose (TDD): 1-1.5 mg PO given in divided doses over 1
d Maintenance dose: 0.125-0.375 mg/d PO qd or divided bid |
| Pediatric Dose | Total
digitalizing dose (TDD): Premature infants: 0.02 mg/kg PO divided q8h Full-term infants: 0.03 mg/kg PO divided q8h 1-24 months: 0.04-0.05 mg/kg PO divided q8h >2 years: 0.03-0.04 mg/kg PO divided q8h Maintenance dose: Infants: 6-8 mcg/kg/d PO >2-5 years: 10-15 mcg/kg/d PO >5-10 years: 7 to 10 mcg/kg/d PO >10 years: 3-5 mcg/kg/d PO <10 years: Recommend daily maintenance dose be divided bid |
| Contraindications | Documented hypersensitivity; beriberi heart disease, idiopathic hypertrophic subaortic stenosis, constrictive pericarditis, carotid sinus syndrome |
| Interactions | Possibility
of increased digoxin levels with alprazolam, benzodiazepines,
bepridil, captopril, cyclosporine, propafenone, propantheline,
quinidine, diltiazem, aminoglycosides, oral amiodarone,
anticholinergics, diphenoxylate, erythromycin, felodipine,
flecainide, hydroxychloroquine, itraconazole, nifedipine,
omeprazole, quinine, ibuprofen, indomethacin, esmolol,
tetracycline, tolbutamide, and verapamil Possibility of decreased serum digoxin levels with aminoglutethimide, antihistamines, cholestyramine, neomycin, penicillamine, aminoglycosides, oral colestipol, hydantoins, hypoglycemic agents, antineoplastic treatment combinations (including carmustine, bleomycin, methotrexate, cytarabine, doxorubicin, cyclophosphamide, vincristine, and procarbazine), aluminum or magnesium antacids, rifampin, sucralfate, sulfasalazine, barbiturates, kaolin/pectin, and aminosalicylic acid |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Hypokalemia may reduce positive inotropic effect of digitalis; IV calcium may produce arrhythmias in digitalized patients; hypercalcemia predisposes patient to digitalis toxicity, and hypocalcemia can make digoxin ineffective until serum calcium levels are normal; magnesium replacement therapy must be instituted in patients with hypomagnesemia to prevent digitalis toxicity; patients diagnosed with incomplete AV block may progress to complete block when treated with digoxin; caution in hypothyroidism, hypoxia, and acute myocarditis |
| Drug Name |
Amoxicillin (Amoxil, Trimox) -- Interferes with synthesis of cell wall mucopeptides during active multiplication resulting in bactericidal activity against susceptible bacteria. Used as prophylaxis in minor procedures. |
|---|---|
| Adult Dose | 2 g PO 1
h before the procedure Alternatively, 3 g PO 1 h before the procedure, followed by 1.5 g 6 h after the initial dose |
| Pediatric Dose | 50 mg/kg PO 1 h before the procedure; not to exceed 2 g/dose |
| Contraindications | Documented hypersensitivity |
| Interactions | Reduces the efficacy of oral contraceptives |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in renal impairment |
| Drug Name |
Ampicillin (Marcillin, Omnipen) -- For prophylaxis in patients undergoing dental, oral, or respiratory tract procedures. |
|---|---|
| Adult Dose | 2 g IV/IM
30 min before procedure High-risk patients: 2 g ampicillin IV/IM plus gentamicin 1.5 mg/kg IV 30 min before procedure, followed 6 h later by 1 g ampicillin IV/IM or 1 g amoxicillin PO |
| Pediatric Dose | 50-mg/kg
IV/IM 30 min before procedure; not to exceed 2 g/dose High-risk patients: 50 mg/kg IV/IM ampicillin plus gentamicin 1.5 mg/kg IV 30 min before procedure, followed 6 h later by ampicillin 25 mg/kg IV/IM or amoxicillin 25 mg/kg PO |
| Contraindications | Documented hypersensitivity |
| Interactions | Probenecid and disulfiram elevate levels; allopurinol decreases ampicillin effects and has additive effects on ampicillin rash; may decrease effects of oral contraceptives |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in renal failure; evaluate rash and differentiate from hypersensitivity reaction |
| Drug Name |
Clindamycin (Cleocin) -- Used in penicillin allergic patients undergoing dental, oral, or respiratory tract procedures. Useful for treatment against streptococcal and most staphylococcal infections. |
|---|---|
| Adult Dose | 600 mg PO/IV 1 h before procedure and 150 mg PO/IV 6 h after first dose |
| Pediatric Dose | 20 mg/kg PO 1h or 20 mg/kg IV 30 min before the procedure; not to exceed 600 mg/dose |
| Contraindications | Documented hypersensitivity; regional enteritis, ulcerative colitis, hepatic impairment, antibiotic-associated colitis |
| Interactions | Increases duration of neuromuscular blockade, induced by tubocurarine and pancuronium; erythromycin may antagonize effects of clindamycin; antidiarrheals may delay absorption of clindamycin |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; associated with severe and possibly fatal colitis |
| Drug Name |
Gentamicin (Garamycin) -- Aminoglycoside antibiotic for gram-negative coverage. Used in combination with both an agent against gram-positive organisms and one that covers anaerobes. Used in conjunction with ampicillin or vancomycin for prophylaxis in GI or genitourinary procedures. |
|---|---|
| Adult Dose | 1.5 mg/kg IV; not to exceed 120 mg/dose; administer with ampicillin 2 g IV 30 min before procedure |
| Pediatric Dose | 1.5 mg/kg IV; not to exceed 120 mg/dose with ampicillin (50 mg/kg; not to exceed 2 g/dose) 30 min before procedure |
| Contraindications | Documented hypersensitivity, non—dialysis-dependent renal insufficiency |
| Interactions | Coadministration with other aminoglycosides, cephalosporins, penicillins, and amphotericin B may increase nephrotoxicity; aminoglycosides enhance effects of neuromuscular blocking agents thus prolonged respiratory depression may occur; coadministration with loop diuretics may increase auditory toxicity of aminoglycosides; possible irreversible hearing loss of varying degrees may occur (monitor regularly) |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Narrow therapeutic index (not intended for long-term therapy); caution in renal failure (not on dialysis), myasthenia gravis, hypocalcemia, and conditions that depress neuromuscular transmission; adjust dose in renal impairment |
| Drug Name |
Vancomycin (Vancocin) -- Potent antibiotic directed against gram-positive organisms and active against Enterococcus species. Useful in the treatment of septicemia and skin structure infections. Indicated for patients who cannot receive, or have failed to respond to penicillins and cephalosporins or have infections with resistant staphylococci. |
|---|---|
| Adult Dose | Dental,
oral or upper respiratory tract surgery: 1 g IV, infused over 1 h,
1 h prior to the procedure GI/GU procedures: 1 g IV plus gentamicin 1.5 mg/kg IV infused over 1 h, 1 h before surgery |
| Pediatric Dose | Dental, oral or upper respiratory tract surgery: 20 mg/kg IV, infused over 1 h, 1 h before the procedure; not to exceed 1 g/dose |
| Contraindications | Documented hypersensitivity |
| Interactions | Erythema, histaminelike flushing and anaphylactic reactions may occur when administered with anesthetic agents; taken concurrently with aminoglycosides, risk of nephrotoxicity may increase above that with aminoglycoside monotherapy; effects in neuromuscular blockade may be enhanced, when coadministered with nondepolarizing muscle relaxants |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Renal failure, neutropenia; red man syndrome is caused by too rapid IV infusion (dose given over a few min) but rarely happens when dose given as 2-h administration or as PO or IP administration; red man syndrome is not an allergic reaction |
| Drug Name |
Cefazolin (Ancef) -- First-generation semisynthetic cephalosporin that arrests bacterial cell wall synthesis, inhibiting bacterial growth. Primarily active against skin flora, including Staphylococcus aureus. |
|---|---|
| Adult Dose | 1 g IV/IM or IV within 30 min before procedure |
| Pediatric Dose | 25 mg/kg IV/IM within 30 min before procedure; not to exceed 1 g/dose |
| Contraindications | Documented hypersensitivity |
| Interactions | Probenecid prolongs effect of cefazolin; coadministration with aminoglycosides, may increase renal toxicity; may yield false-positive urine-dip test results for glucose |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in renal impairment; superinfections, and promotion of nonsusceptible organisms may occur with prolonged use or repeated therapy |
| Drug Name |
Cephalexin (Keflex) -- First-generation cephalosporin arrests bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal activity against rapidly growing organisms. Primary activity against skin flora and used for skin infections or prophylaxis in minor procedures. |
|---|---|
| Adult Dose | 2 g PO 1h before procedure |
| Pediatric Dose | 50 mg/kg PO 1h before procedure; not to exceed 2 g/dose |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration with aminoglycosides increase nephrotoxic potential |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in renal impairment |
| Drug Name |
Cefadroxil (Duricef) -- First-generation cephalosporin arrests bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal activity against rapidly growing organisms. Primary activity against skin flora and used for skin infections or prophylaxis in minor procedures. |
|---|---|
| Adult Dose | 2 g PO 1h before procedure |
| Pediatric Dose | 30 mg/kg PO 1h before procedure; not to exceed 2 g/dose |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration with furosemide or aminoglycosides may increase nephrotoxicity; probenecid prolongs effects |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Adjust dose in renal impairment; superinfections, and promotion of nonsusceptible organisms may occur with prolonged use or repeated therapy |
| Drug Name |
Clarithromycin (Biaxin) and azithromycin (Zithromax) -- These agents inhibit bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes causing RNA-dependent protein synthesis to arrest. |
|---|---|
| Adult Dose | Clarithromycin and azithromycin: 500 mg PO 1 h before procedure |
| Pediatric Dose | Clarithromycin and azithromycin: 15 mg/kg PO 1 h before procedure; not to exceed 500 mg/dose |
| Contraindications | Documented hypersensitivity; coadministration of pimozide |
| Interactions | Clarithromycin
inhibits CYP450 3A4, azithromycin has not demonstrated to inhibit
CYP450 isoenzymes; clarithromycin toxicity increases with coadministration of fluconazole, astemizole and pimozide; clarithromycin effects decrease and GI adverse effects may increase with coadministration of rifabutin or rifampin; may increase toxicity of anticoagulants, cyclosporine, tacrolimus, digoxin, omeprazole, carbamazepine, ergot alkaloids, triazolam, HMG CoA-reductase inhibitors; cardiac arrhythmias may occur with coadministration of cisapride; plasma levels of certain benzodiazepines may increase, prolonging CNS depression; arrhythmias and increase in QTc intervals occur with disopyramide; coadministration with omeprazole may increase plasma levels of both agents |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Coadministration with ranitidine or bismuth citrate is not recommended with CrCl <25 mL/min; give half dose or increase dosing interval if CrCl <30 mL/min; diarrhea may be sign of pseudomembranous colitis; superinfections may occur with prolonged or repeated antibiotic therapies |
FOLLOW-UP
Further Inpatient Care:
- Admit the patient to the hospital for either cardiac catheterization or surgical treatment.
- Adjunctive therapeutic measures
- Administer potassium supplements to all patients receiving furosemide or thiazide diuretics.
- Restrict physical activity in symptomatic patients.
- Place patients with severe pulmonary venous congestion in the sitting or propped-up position.
- Administer parenteral morphine in patients with pulmonary edema to help relieve anxiety and reduce pulmonary congestion.
- Administer oxygen by a nasal catheter or mask to improve oxygenation in acute pulmonary edema.
- Vigorously treat concurrent infections or other aggravating factors.
- Correct anemia if present. Increase the oxygen carrying capacity by a packed-cell transfusion to give considerable relief in patients with severe symptoms of CHF.
- Counsel all patients with supravalvar mitral ring concerning the need for antibiotic prophylaxis against infective endocarditis when they undergo any dental or surgical procedure.
Further Outpatient Care:
- Provide follow-up care on an outpatient basis for monitoring symptoms, compliance with treatment, dose requirement, and for early recognition of adverse drug effects. Periodically check the serum electrolyte levels and renal function for patients on diuretics. Prompt detection and treatment of intercurrent infections, arrhythmia, and other complications helps to reduce morbidity and prevent worsening of CHF.
In/Out Patient Meds:
- Continue treatment with diuretics and digoxin in patients with supravalvar mitral ring and CHF. Recommend a potassium supplement, especially for children on furosemide therapy. Antibiotics are necessary for intercurrent bacterial infections and for prophylaxis of infective endocarditis during dental or surgical procedures.
Transfer:
- Transfer to a tertiary cardiac center for further diagnostic evaluation and surgical correction.
Deterrence/Prevention:
- Symptomatic patients with supravalvar mitral ring should avoid sports and other strenuous activity that could aggravate pulmonary congestion and CHF.
Complications:
- Possible complications of supravalvar mitral ring include pulmonary edema, pulmonary arterial hypertension, atrial arrhythmia, left atrial thrombus, embolic episodes, recurrent pulmonary infections, and infective endocarditis.
Prognosis:
- Isolated supravalvar mitral ring is a rare defect that usually is correctable by surgery. The presence of a normal underlying mitral valve and absence of other major cardiac lesions is associated with a better surgical outcome than with abnormal valve tissue.
- The prognosis is poor in patients who require resection at an early age. Mortality is high, with risk of recurrent supravalvar mitral stenosis in survivors, probably because of continuing turbulence across the small LV inflow tract.
Patient Education:
- Educate the patient and family on the importance of regular medical treatment, periodic medical review, restriction of heavy physical exertion, need for antibiotic prophylaxis during dental and surgical procedures, and the need to promptly attend to all infections.
MISCELLANEOUS
Medical/Legal Pitfalls:
- Failure to recognize supravalvar mitral ring as an associated defect in patients with coarctation or subaortic stenosis
- Failure to recognize associated abnormalities of the mitral valve and left ventricular outflow tract in patients with supravalvar mitral ring
- Failure to identify the presence of a supravalvar mitral ring in patients with symptoms and signs of mitral stenosis
Special Concerns:
- Supravalvar mitral ring may not be easily detectable in children with CHD; therefore, awareness of the problem and careful echocardiographic screening are important in all children with CHD.
PICTURES
| Caption: Picture 1. Mitral stenosis, supravalvular ring. Seen here is a 2-dimensional echocardiogram in parasternal long-axis view showing a supravalvar mitral ring (small arrows) close to and adherent to the mitral valve leaflet (large arrow). The ring and the restricted opening of the mitral valve cause mitral obstruction. A large ventricular septal defect also is present. LA = left atrium, LV = left ventricle, AO = aorta, RV = right ventricle. |
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| Picture Type: Photo |
| Caption: Picture 2. Mitral stenosis, supravalvular ring. Seen here is a 2-dimensional echocardiogram with color flow imaging in the parasternal long-axis view showing turbulent flow (arrow) in diastole from left atrium (LA) to left ventricle (LV), caused by an obstructive supravalvar mitral ring. RV = right ventricle. |
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| Picture Type: Photo |
| Caption: Picture 3. Mitral stenosis, supravalvular ring. This 2-dimensional echocardiogram in the apical view shows the supravalvar mitral ring (small arrows) adherent to the mitral valve leaflet (large arrow). LA = left atrium, LV = left ventricle, RA = right atrium, RV = right ventricle. |
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| Picture Type: Photo |
| Caption: Picture 4. Mitral stenosis, supravalvular ring. This image is a 2-dimensional echocardiogram with color flow imaging in apical view showing turbulent flow (arrow) in diastole from left atrium (LA) to left ventricle (LV), caused by an obstructive supravalvar mitral ring. RA = right atrium, RV = right ventricle. |
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| Picture Type: Photo |
| Caption: Picture 5. Mitral stenosis, supravalvular ring. Simultaneous recording of pressures in the pulmonary artery wedge position (PAW) and the left ventricle (LV) shows a large gradient in diastole across the mitral valve. The PAW pressure is markedly elevated. |
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| Picture Type: Graph |
| Caption: Picture 6. Mitral stenosis, supravalvular ring. Shown here is an M-mode echocardiogram of the mitral valve in a patient with supravalvar mitral ring causing obstruction. The mitral valve leaflets show diminished excursion and a markedly reduced E-F slope in diastole. RV = right ventricle, LV = left ventricle, MV = mitral valve. |
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| Picture Type: Photo |